I saw this question, but I didn\'t see a JavaScript specific example. Is there a simple string.Empty
available in JavaScript, or is it just a case of checking f
The closest thing you can get to str.Empty
(with the precondition that str is a String) is:
if (!str.length) { ...
You could also go with regular expressions:
if((/^\s*$/).test(str)) { }
Checks for strings that are either empty or filled with whitespace.
Very generic "All-In-One" Function (not recommended though):
function is_empty(x)
{
return ( //don't put newline after return
(typeof x == 'undefined')
||
(x == null)
||
(x == false) //same as: !x
||
(x.length == 0)
||
(x == 0) // note this line, you might not need this.
||
(x == "")
||
(x.replace(/\s/g,"") == "")
||
(!/[^\s]/.test(x))
||
(/^\s*$/.test(x))
);
}
However, I don't recommend to use that, because your target variable should be of specific type (i.e. string, or numeric, or object?), so apply the checks that are relative to that variable.
var s; // undefined
var s = ""; // ""
s.length // 0
There's nothing representing an empty string in JavaScript. Do a check against either length
(if you know that the var will always be a string) or against ""
All these answers are nice.
But I cannot be sure that variable is a string, doesn't contain only spaces (this is important for me), and can contain '0' (string).
My version:
function empty(str){
return !str || !/[^\s]+/.test(str);
}
empty(null); // true
empty(0); // true
empty(7); // false
empty(""); // true
empty("0"); // false
empty(" "); // true
Sample on jsfiddle.
I would not worry too much about the most efficient method. Use what is most clear to your intention. For me that's usually strVar == ""
.
As per the comment from Constantin, if strVar could some how end up containing an integer 0 value, then that would indeed be one of those intention-clarifying situations.